Background Image vs Reference Image - What are the pros and cons of these methods?
To view through the selected camera press numpad 0.
To align the Reference image with the camera view, select the Reference image, then in the header menu &gt; Object &gt; Transform &gt; Align to Transform Orientation then in the Operator box choose Orientation &gt; View.
Reference and Background are empties, they won't be rendered, they are used as references to model an object, liked the former Background in 2.79.
Actually they are exactly the same objects, except that the default settings in the Properties panel &gt; Object Data are not the same, by default Background will only be seen in orthographic view and it is set to have its back transparent (but you can switch off these 2 options or switch them on for a Reference image).
What's the difference? I guess it all depends on what settings make you comfortable to work with. The Background version works a bit more like the former Background in 2.79, it makes the image more discrete and transparent in your scene, and if you enable its Only Axis Aligned you'll see it only in perpendicular views, which is very convenient.